c# - Linq Join: Join using a mapping table and associate objects -

i trying write linq query make basic join. have 2 arrays

park[] parks = new park[]{                 new park() {id = 1, name = "free park"},                 new park() {id = 2, name = "cost park"},                 new park() {id = 3, name="sneak in park"} }; 

and

facility[] facilities = new facility[] {                 new facility() { id = 1, name = "swing", minimumage = 1, maximumage = 120},                 new facility() { id = 2, name = "slide", minimumage = 1, maximumage = 200},                 new facility() { id = 3, name = "see-saw", minimumage = 1, maximumage = 300} }; 

each park can have 0...n facilities, hence have set of mapping objects

parkfacility[] associations = new parkfacility[] {                 new parkfacility() {parkid = 1, facilityid = 1},                 new parkfacility() {parkid = 1, facilityid = 2},                 new parkfacility() {parkid = 1, facilityid = 3},                 new parkfacility() {parkid = 2, facilityid = 1},                 new parkfacility() {parkid = 3, facilityid = 2} }; 

this definition of class park

class park {         public int id { get; set; }         public string name { get; set; }         public facility[] facilities { get; set; } } 

is possible use joins , associate appropriate facilities parks? i.e. set facilities array in park appropriately mapped using associations?

edit: research far..

var x_temp = g in parks              join j in associations on g.id equals j.parkid h              select new park()              {                 name = g.name,                 id = g.id,                 facilities = (from u in h join m in facilities on u.facilityid equals m.id select m).toarray()              }; 

i tried using sub-linq query , works, looking solution only joins

you can create lookup park id facilities, , use populate facilities property on each of park objects. note best place in constructor of park, in keeping existing code snippet in object initializer:

var lookup = associations.tolookup(pf => pf.parkid, pf => facilities.single(f => f.id == pf.facilityid)); park[] parks = new park[]{     new park() {id = 1, name = "free park", facilities = lookup[1].toarray()},     new park() {id = 2, name = "cost park", facilities = lookup[2].toarray()},     new park() {id = 3, name="sneak in park", facilities = lookup[3].toarray()} }; 

additionally, helpful store facility , park instances in dictionary mapping id instance. in case lookup wouldn't need linear scan through facilities each association.